We propose to continue our research on the[unreadable] function of the endothelial storage granules called Weibel-Palade bodies (WPBs)[unreadable] and also include studies of the related platelet granules. We will explore the role of these granules both in homeostasis and in mouse disease models of acute and chronic inflammation, thrombotic thrombocytopenic purpura and stroke. The project will consist of three interrelated Specific Aims. In the first Aim, new roles of Weibel-Palade body components in inflammation and wound healing will be ad[unreadable] dressed. We propose to examine the role of von Willebrand factor (VWF) in leukocyte adhesion and recruitment to sites of inflammation. This is based on our documentation of increased leukocyte rolling in mice lacking the metalloprotease ADA[unreadable] MTS13 which reduces the biological activity of secreted VWF. We also propose to[unreadable] explore the vascular functions of Angiopoietin-2 (Ang-2), a recently recognized[unreadable] component of WPBs. Using Ang-2 -/- mice, we will address the role of Ang-2 in wound healing and inflammatory responses including lymphangiogenesis. In the second aim, we will perform studies of vessels during inflammation and the role of platelet and endothelial granules in vessel stability and prevention of hemorrhage[unreadable] . This aim is based on our surprising observation of massive hemorrhage in micro[unreadable] circulation at sites of inflammation in thrombocytopenic mice. We will evaluate[unreadable] the role of platelet adhesion, platelet microparticles and platelet granules in[unreadable] endothelial stabilization. Emphasis will be given to the importance of the balance between platelet Angiopoietin-1 and vascular Angiopoietin-2, molecules regulating vascular stability in opposing ways, and the possible role of platelet serotonin in preventing inflammatory hemorrhage. In addition, the function of platelet serotonin in inflammation, angiogenesis and wound healing will be studied in[unreadable] mice deficient in a key enzyme needed for peripheral serotonin production, tryptophan hydroxylase 1. In the third aim we will examine the role of Weibel-Palade[unreadable] bodies and ADAMTS13 in stroke and stroke recovery. This aim is based on the fact[unreadable] that ischemia/reperfusion, such as occurs in thrombotic stroke, induces WPB secretion and on our preliminary result pointing to an important role for VWF in stroke-induced injury. We will examine the effect of elevated plasma VWF and ADAMT[unreadable] S13-deficiency on the outcome of stroke and test recombinant ADAMTS13 as a new candidate for stroke therapy. We will also explore the role of Angiopoietin-2 in[unreadable] stroke injury, stroke-induced angiogenesis and recovery from brain injury. We hope that our studies will further clarify the role of WPBs in normal tissue repair and in inflammatory and thrombotic diseases. The components of WPBs are key targets for drug development. Thus an exact understanding of their involvement in[unreadable] these processes is essential. PUBLIC HEALTH RELEVANCE: We propose to study the function of molecules stored in Weibel-Palade bodies, vesicles within the cells of blood vessels. The contents of these vesicles are released during injury where[unreadable] the released molecules help in tissue repair. The Weibel-Palade bodies are also[unreadable] released in pathological situations and then they promote heart disease, inflammation and stroke. We will investigate how inhibition of a particular component[unreadable] of these vesicles could improve outcome in these major diseases. [unreadable]